Troubleshooting Guide - Millivolt - Lennox MLDVT-30NM Care And Operation Instructions Manual

LENNOX HEARTH PRODUCTS • MERIT
TROUBLESHOOTING GUIDE: MILLIVOLT GAS CONTROL SYSTEM
Note: Before troubleshooting the gas control system, make sure the external gas shut off valve (located at gas supply inlet) is in the
"ON" position.
Note: Valve system troubleshooting should only be performed by a qualified service technician.
SYMPTOM
1. Spark igniter will
not light pilot after
repeated triggering
of igniter button.
WARNING: if the
pilot will not light
after 1 minute of
attempting, wait for
at least 5 minutes for
gas to clear before
attempting again.
2. Pilot will not stay
lit after carefully
following the lighting
instructions.
3. Pilot burning, no
gas to burner, Valve
knob "ON," and the
(standard) burner
OFF/ON switch is
"ON."
NOTE: If an optional*
remote switch is
used for burner
operation, if the
standard burner
OFF/ON switch is
still installed on
appliance it must be
in the "OFF" position.
4. Frequent pilot/burner
outage problem.
* Optional remote switch kits—wall switch, wall thermostat or remote control.
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SERIES DIRECT-VENT GAS FIREPLACES • MODELS MLDVT-30/35/40/45 • CARE AND OPERATION INSTRUCTIONS
®
POSSIBLE CAUSES
A. Defective igniter
(no spark at electrode).
B. Defective or misaligned
electrode at pilot (spark at
electrode).
C. Gas supply pressure
errant.
D. Pilot orifice plugged.
A. Defective pilot generator
(thermocouple).
A. Wall switch or wires
defective.
B. Thermopile may not be
generating sufficient
millivolts.
C. Plugged burner orifice.
D. OFF/ON Switch and
*Remote Switch are in the
"ON" position resulting in
excessive resistance.
A. Pilot flame may be too low
or blowing (high) causing
the pilot/valve safety to
drop out.
Check for spark at electrode and pilot; if no spark and electrode wire is properly
connected, replace igniter.
Using a match, light pilot. If pilot lights, turn off pilot and trigger the igniter button
again. If pilot lights, an improper gas mixture caused the bad lighting and a longer
purge period is recommended. If pilot will not light – check gap at electrode and
pilot – should be 1/8" to have a strong spark. If gap measures 1/8", replace pilot (see
Figure 14 on Page 16).
Check inlet gas pressure. It should be within the limits as marked on the rating plate.
Clean or replace pilot orifice.
Check pilot flame, it must impinge on thermocouple (see Figure 14 on Page 16).
Clean and/or adjust pilot for maximum flame impingement on thermocouple. Ensure
that the connection between the valve and thermocouple are tight and secure.
Check wall switch and wires for proper connections. Jumper wire across terminals at
wall switch, if burner comes on, replace defective wall switch. If okay, jumper wires
across wall switch wires at valve, if burner comes on, wires are faulty or connections
are bad.
Check thermopile with millivolt meter. Take reading at thermopile terminals of gas
valve. Should read 325 millivolts minimum with optional wall switch "OFF." Replace
faulty thermopile if reading is below specified minimum.
Check burner orifice for blockage and remove.
When turning on the burner using a *remote switch, ensure that the standard OFF/ON
switch is in the "OFF" position. If both switches are in the ON position, it may result in
excessive resistance (and millivolt drainage) and the burner may not come on.
Clean and/or adjust pilot flame for maximum flame impingement on thermocouple
(see Figure 14 on Page 16).
CORRECTIVE ACTION